Erythropoietin (EPO), a well known glycoprotein was originally identified for its hormonal effects on the bone marrow and is involved in the growth and development of mature red blood cells. In addition to this hematopoietic activity it has recently been discovered that EPO also functions as a potent, locally produced molecule ameliorating metabolic stress in many tissues. The tissue protective activities of EPO are mediated through interaction with the erythropoietin receptor. In the brain, for example, EPO and its receptor are locally produced, modulated by metabolic stressors, and provide neuroprotective and anti-inflammatory functions (Doggrell, S A. (2004) Expert Opin Investig Drugs; 13(11):1517-9). In the spinal cord, EPO provides beneficial effects including inhibition of apoptosis and necrosis of neurons, oligodendrocytes and endothelial cells, less cavitations, reduction of lipid peroxidation, mobilization of endothelial progenitor cells, promotion of angiogenesis and restoration of vascular autoregulation (Gorio, A. et al (2002) Proc Natl Acad Sci USA; 99(14):9450-5; Leist M. (2004) Science; 305(5681):239-42). EPO has been shown to signal through modulation of members of the nuclear factor (NF)-kappaB pathway as well as by the janus kinase-2/signal transducers and activators of transcription-5 system (Gorio A. (2005) Neurosurgery; 56(4):821-7; Grasso G. (2005) Neurosurgery; 56(4):821-7).
By chemical modification, i.e. carbamoylation of at least one primary amino group of the lysines and/or of the N-terminal amino acid of EPO the hematopoietic activity of this cytokine is considerably reduced while its tissue protective activity, i.e. its nerval cell regenerative activity remains substantially unaltered or is even enhanced as compared to uncarbamoylated EPO.
WO 2006/014466 and WO 2006/002646 disclose the manufacture and use of carbamoylated EPO for various medical indications.
Since EPO has a relatively short serum half-life and since it is well known in the art that the fusion of an immunoglobulin constant region to a non-immuno-globulin protein can markedly prolong the serum half-life of said non-immuno-globulin protein, several approaches have been made linking an immunoglobulin fragment to EPO. For example, WO 99/02709 discloses the production and use of fusion proteins comprising EPO and an Fc portion of an immunoglobulin, wherein the EPO-Fc fusion proteins have an increased in vivo half-life relative to naturally occurring EPO.
From WO2005/063808 it is known that a further improvement of the pharmacokinetics, i.e. prolonged serum half-lives and increased in vivo potency of EPO-Fc fusion proteins can be obtained by mutations, deletions or insertions of specific amino acids.
Accordingly, there is a need for a simplified and less costly EPO therapy, i.e. requiring less frequent EPO administration, for the treatment of diseases, wherein an unaltered or even enhanced tissue regenerative activity, i.e. the nerve cell regenerative activity of EPO, is desirable while simultaneously the hematopoietic activity of EPO is less desirable or is even undesired and shall thus be reduced. Such diseases include but are not limited to malfunctions or impairments of either or both the central (CNS) and peripheral (PNS) nervous systems, and particularly include diseases that are associated with or caused by injuries to the CNS and/or PNS such as physical damages following, for example, a mechanical impact.